1. Field of the Invention
This invention relates to rotary saws, and in particular to a guide assembly using hydro-dynamic pressure lubrication for a plurality of circular saw blades fixed on an arbor.
2. Prior Art
The laws of lubrication, which are well established, apply without exception to saw guiding. If the lubricants supplied to the saw guide surface and, the surface which is in intimate contact with the rotating saw blade surface is intermittent or inadequate, a form of lubrication sometimes referred to as boundary or partial lubrication, occurs. In this case excessive wear of the guiding surface is prevented primarily by adhesion of lubricant to the surface and by selection of a low-friction material for the guiding surface. With this type of saw guide a liquid lubricant for which water is preferred is always required. However, because of only partial lubrication, a generally excessive quantity of water is required.
On the other hand, if a continuous film of lubricant is established between the saw guide and the saw blade and its film is stable, that is, it does not disappear intermittently, then air becomes a very excellent lubricant as it provides a higher load bearing capability. In saw guiding, liquid lubricants are not preferred because of the attendant relatively high consumption. Contrary to bearing lubrication, in saw guiding it is impractical to recirculate the lubricant within a closed system.
Techniques of using air or other lubricants are not new, but present systems, because of their design, do not establish stable air films and thus require excessive amounts of liquid lubricants.
Furthermore, present designs all rely upon one side of a saw guide being fixed. The saw references against the fixed side and the other side is either also fixed or floating. When a saw is rigidly mounted in collars, any small mis-alignment between the fixed saw and the fixed guide causes the hydro-dynamic film lubrication to break down, i.e. a diverging film of lubrication would be established. This is a problem that is well understood and was solved in bearing designs by allowing the guide surfaces or pads to tilt. Present guide systems, therefore, because of this problem are nearly always used with floating saws so that the saw blade itself will then align itself with the guide pad. Floating saw blades, however, which are normally guided by two or three small guide pads do not have the advantage of rigidly fixed saw blades as lateral stiffness of the latter saw measured in the tooth region is considerably greater than in a floating saw blade.